#include<stdio.h>
#include<math.h>
int main()
{
    int num[1005];
    //freopen("in.txt","r",stdin);
    int n;
    while (scanf("%d",&n) != EOF && n != 0)
    {
        double average = 0;
        double s = 0;
        for(int i = 0; i < n; i++)
        {
            scanf("%d",&num[i]);
            average += num[i];
        }
        average = average / n;
        //printf("%f\n",average);
        for(int i = 0; i < n; i++)
        {
            s += (num[i] - average) * (num[i] - average);
        }
        s = s/n;
        printf("%.8f\n",sqrt(s));
    }
    
}